Error Handling and Diagnostics

An application program must anticipate runtime errors and attempt to recover from them. This chapter provides an in-depth discussion of error reporting and recovery. You learn how to handle warnings and errors using the status variables SQLCODE, SQLSTATE, and SQLCA (SQL Communications Area), and the WHENEVER statement. You also learn how to diagnose problems using the status variable ORACA (Oracle Communications Area). The following topics are discussed:

the need for error handling

error handling alternatives

using status variables when MODE={ANSI|ANSI14}

using the SQL Communications Area

using the Oracle Communications Area

The Need for Error Handling

A significant part of every application program must be devoted to error handling. The main benefit of error handling is that it allows your program to continue operating in the presence of errors. Errors arise from design faults, coding mistakes, hardware failures, invalid user input, and many other sources

You cannot anticipate all possible errors, but you can plan to handle certain kinds of errors meaningful to your program. For the Oracle Precompilers, error handling means detecting and recovering from SQL statement execution errors.

You can also prepare to handle warnings such as "value truncated" and status changes such as "end of data." It is especially important to check for error and warning conditions after every data manipulation statement, because an INSERT, UPDATE, or DELETE statement might fail before processing all eligible rows in a table.

Error Handling Alternatives

The Oracle Precompilers provide four status variables that serve as error handling mechanisms:

SQLCODE (SQLCOD in Pro*FORTRAN)

SQLSTATE (SQLSTA in Pro*FORTRAN)

SQLCA (using the WHENEVER statement)

ORACA

The MODE option (described ) governs ANSI/ISO compliance. The availability of the SQLCODE, SQLSTATE, and SQLCA variables depends on the MODE setting. You can declare and use the ORACA variable regardless of the MODE setting. For more information, see "Using the Oracle Communications Area" .

When MODE={ORACLE|ANSI13}, you must declare the SQLCA status variable. SQLCODE and SQLSTATE declarations are accepted (not recommended) but are not recognized as status variables. For more information, see "Using the SQL Communications Area" .

When MODE={ANSI|ANSI14}, you can use any one, two, or all three of the SQLCODE, SQLSTATE, and SQLCA variables. To determine which variable (or variable combination) is best for your application, see "Using Status Variables when MODE={ANSI|ANSI14}" .

SQLCODE stores error codes and the "not found" condition. It is retained only for compatibility with SQL89 and is likely to be removed from future versions of the standard.

Unlike SQLCODE, SQLSTATE stores error and warning codes and uses a standardized coding scheme. After executing a SQL statement, the Oracle server returns a status code to the SQLSTATE variable currently in scope. The status code indicates whether a SQL statement executed successfully or raised an exception (error or warning condition). To promote interoperability (the ability of systems to exchange information easily), SQL92 predefines all the common SQL exceptions.

SQLCA

The SQLCA is a record-like, host-language data structure. Oracle updates the SQLCA after every executable SQL statement. (SQLCA values are undefined after a declarative statement.) By checking Oracle return codes stored in the SQLCA, your program can determine the outcome of a SQL statement. This can be done in two ways:

implicit checking with the WHENEVER statement

explicit checking of SQLCA variables

You can use WHENEVER statements, code explicit checks on SQLCA variables, or do both. Generally, using WHENEVER statements is preferable because it is easier, more portable, and ANSI-compliant.

ORACA

When more information is needed about runtime errors than the SQLCA provides, you can use the ORACA, which contains cursor statistics, SQL statement data, option settings, and system statistics.

The ORACA is optional and can be declared regardless of the MODE setting. For more information about the ORACA status variable, see "Using the Oracle Communications Area" .

Using Status Variables when MODE={ANSI|ANSI14}

When MODE={ANSI|ANSI14}, you must declare at least one -- you may declare two or all three -- of the following status variables:

SQLCODE

SQLSTATE

SQLCA

In Pro*COBOL, you cannot declare SQLCODE if SQLCA is declared. Likewise, you cannot declare SQLCA if SQLCODE is declared. The field in the SQLCA data structure that stores the error code for Pro*COBOL is also called SQLCODE, so errors will occur if both status variables are declared.

Your program can get the outcome of the most recent executable SQL statement by checking SQLCODE and/or SQLSTATE explicitly with your own code after executable SQL and PL/SQL statements. Your program can also check SQLCA implicitly (with the WHENEVER SQLERROR and WHENEVER SQLWARNING statements) or it can check the SQLCA variables explicitly.

Note: When MODE={ORACLE|ANSI13}, you must declare the SQLCA status variable. For more information, see "Using the SQL Communications Area" .

Some Historical Information

The treatment of status variables and variable combinations by the Oracle Precompilers has evolved beginning with Release 1.5.

Release 1.5

The Oracle Precompilers, Release 1.5, presumed there was a status variable SQLCODE whether or not it was declared in a Declare Section; in fact, the precompiler never bothered to note whether there was a declaration for SQLCODE or not -- it just presumed one existed. SQLCA would be used as a status variable if and only if there was an INCLUDE of the SQLCA.

Release 1.6

Beginning with Oracle Precompilers, Release 1.6, the precompilers no longer presume that there is a SQLCODE status variable and it is not required. The precompiler requires that at least one of SQLCA, SQLCODE, or SQLSTATE be declared.

SQLCODE is recognized as a status variable if and only if at least one of the following criteria is satisfied:

It is declared in a Declare Section with exactly the right datatype.

The precompiler finds no other status variable.

If the precompiler finds a SQLSTATE declaration (of exactly the right type of course) in a Declare Section or finds an INCLUDE of the SQLCA, it will not presume SQLCODE is declared.

Release 1.7

Because Release 1.5 of the Oracle Precompilers allowed the SQLCODE variable to be declared outside of a Declare Section while also declaring SQLCA, precompilers Release 1.6 and greater are presented with a compatibility problem. A new option, ASSUME_SQLCODE={YES|NO} (default NO), was added to fix this in Release 1.6.7 and is documented as a new feature in Release 1.7.

When ASSUME_SQLCODE=YES, and when SQLSTATE and/or SQLCA (Pro*FORTRAN only) are declared as status variables, the precompiler presumes SQLCODE is declared whether or not it is declared in a Declare Section or of the proper type. This causes Releases 1.6.7 and later to act like Release 1.5 in this regard. For information about the precompiler option ASSUME_SQLCODE, see "ASSUME_SQLCODE" .

Declaring Status Variables

This section describes how to declare SQLCODE and SQLSTATE. For information about declaring the SQLCA status variable, see "Declaring the SQLCA" .

Declaring SQLCODE

SQLCODE (SQLCOD in Pro*FORTRAN) must be declared as a 4-byte integer variable either inside or outside the Declare Section, as shown in Table 8 - 1.

Language

SQLCODE Declaration

COBOL

SQLCODE PIC S9(9) COMP.

FORTRAN

INTEGER*4 SQLCOD

Table 8 - 1. SQLCODE Declarations

If declared outside the Declare Section, SQLCODE is recognized as a status variable if only if ASSUME_SQLCODE=YES. SQLCODE declarations are ignored when MODE={ORACLE|ANSI13}.

Warning: In Pro*COBOL source files, donot declare SQLCODE if SQLCA is declared. Likewise, donot declare SQLCA if SQLCODE is declared. The status variable declared by the SQLCA structure is also called SQLCODE, so errors will occur if both error-reporting mechanisms are used.

With host languages that allow both local and global declarations, you can declare more than one SQLCODE variable. Access to a local SQLCODE is limited by its scope within your program. After every SQL operation, Oracle returns a status code to the SQLCODE currently in scope. So, your program can learn the outcome of the most recent SQL operation by checking SQLCODE explicitly, or implicitly with the WHENEVER statement.

When you declare SQLCODE instead of the SQLCA in a particular compilation unit, the precompiler allocates an internal SQLCA for that unit. Your host program cannot access the internal SQLCA. If you declare the SQLCA and SQLCODE (not supported in Pro*COBOL), Oracle returns the same status code to both after every SQL operation.

Declaring SQLSTATE

SQLSTATE (SQLSTA in Pro*FORTRAN) must be declared as a five-character alphanumeric string inside the Declare Section, as shown in Table 8 - 2. Declaring the SQLCA is optional.

Language

SQLSTATE Declaration

COBOL

SQLSTATE PIC X(5).

FORTRAN

CHARACTER*5 SQLSTA

Table 8 - 2. SQLSTATE Declarations

When MODE={ORACLE|ANSI13}, declarations of the SQLSTATE variable are ignored.

Status Variable Combinations

When MODE={ANSI|ANSI14}, the behavior of the status variables depends on the following:

and Table 8 - 4 describe the resulting behavior of each status variable combination when ASSUME_SQLCODE=NO and when ASSUME_SQLCODE=YES, respectively.

Declare Section (IN/OUT/ --)SQLCODE SQLSTATE SQLCA

Behavior

OUT

--

--

SQLCODE is declared and is presumed to be a status variable.

OUT

--

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCA is declared as a status variable, and SQLCODE is declared but is not recognized as a status variable.

OUT

--

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

OUT

OUT

--

SQLCODE is declared and is presumed to be a status variable, and SQLSTATE is declared but is not recognized as a status variable.

OUT

OUT

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCA is declared as a status variable, and SQLCODE and SQLSTATE are declared but are not recognized as status variables.

OUT

OUT

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

OUT

IN

--

SQLSTATE is declared as a status variable, and SQLCODE is declared but is not recognized as a status variable.

OUT

IN

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLSTATE and SQLCA are declared as status variables, and SQLCODE is declared but is not recognized as a status variable.

OUT

IN

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

--

--

SQLCODE is declared as a status variable.

IN

--

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE and SQLCA are declared as a status variables.

IN

--

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

OUT

--

SQLCODE is declared as a status variable, and SQLSTATE is declared but not as a status variable.

IN

OUT

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE and SQLCA are declared as a status variables, and SQLSTATE is declared but is not recognized as a status variable.

IN

OUT

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

IN

--

SQLCODE and SQLSTATE are declared as a status variables.

IN

IN

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE, SQLSTATE, and SQLCA are declared as a status variables.

IN

IN

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

--

--

--

This status variable configuration is not supported.

--

--

OUT

SQLCA is declared as a status variable.

--

--

IN

In Pro*COBOL, SQLCA is declared as a status host variable. In Pro*FORTRAN, this status variable configuration is not supported.

--

OUT

--

This status variable configuration is not supported.

--

OUT

OUT

SQLCA is declared as a status variable, and SQLSTATE is declared but is not recognized as a status variable.

--

OUT

IN

In Pro*COBOL, SQLCA is declared as a status host variable, and SQLSTATE is declared but is not recognized as a status variable. In Pro*FORTRAN, this status variable configuration is not supported.

--

IN

--

SQLSTATE is declared as a status variable.

--

IN

OUT

SQLSTATE and SQLCA are declared as status variables.

--

IN

IN

In Pro*COBOL, SQLSTATE and SQLCA are declared as status host variables. In Pro*FORTRAN, this status variable configuration is not supported.

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCA is declared as a status variable, and SQLCODE is declared and is presumed to be a status variable.

OUT

--

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

OUT

OUT

--

SQLCODE is declared and is presumed to be a status variable, and SQLSTATE is declared but is not recognized as a status variable.

OUT

OUT

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCA is declared as a status variable, SQLCODE is declared and is presumed to be a status variable, and SQLSTATE is declared but is not recognized as status variable.

OUT

OUT

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

OUT

IN

--

SQLSTATE is declared as a status variable, and SQLCODE is declared and is presumed to be a status variable.

OUT

IN

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLSTATE and SQLCA are declared as status variables, and SQLCODE is declared and is presumed to be a status variable.

OUT

IN

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

--

--

SQLCODE is declared as a status variable.

IN

--

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE and SQLCA are declared as a status variables.

IN

--

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

OUT

--

SQLCODE is declared as a status variable, and SQLSTATE is declared but not as a status variable.

IN

OUT

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE and SQLCA are declared as a status variables, and SQLSTATE is declared but is not recognized as a status variable.

IN

OUT

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

IN

IN

--

SQLCODE and SQLSTATE are declared as a status variables.

IN

IN

OUT

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, SQLCODE, SQLSTATE, and SQLCA are declared as a status variables.

IN

IN

IN

In Pro*COBOL, this status variable configuration is not supported. In Pro*FORTRAN, this status variable configuration is not supported.

-- -- -- -- -- -- -- -- --

-- -- -- OUT OUT OUT IN IN IN

-- OUT IN -- OUT IN -- OUT IN

These status variable configurations are not supported. SQLCODE must be declared either inside or outside the Declare Section when ASSUME_SQLCODE=YES.

Status Variable Values

This section describes the values for the SQLCODE and SQLSTATE status variables. For information about the SQLCA status variable, see "Key Components of Error Reporting" .

SQLCODE Values

After every SQL operation, Oracle returns a status code to the SQLCODE variable currently in scope. The status code, which indicates the outcome of the SQL operation, can be any of the following numbers:

0

Oracle executed the SQL statement without detecting an error or exception.

> 0

Oracle executed the statement but detected an exception. This occurs when Oracle cannot find a row that meets the condition in your WHERE clause or when a SELECT INTO or FETCH returns no rows.

When MODE={ANSI|ANSI14|ANSI13}, +100 is returned to SQLCODE after an INSERT of no rows. This can happen when a subquery returns no rows to process.

< 0

Oracle did not execute the statement because of a database, system, network, or application error. Such errors can be fatal. When they occur, the current transaction should, in most cases, be rolled back. Negative return codes correspond to error codes listed in Oracle7 Server Messages.

You can learn the outcome of the most recent SQL operation by checking SQLCODE explicitly with your own code or implicitly with the WHENEVER statement.

When you declare SQLCODE instead of the SQLCA in a particular precompilation unit, the precompiler allocates an internal SQLCA for that unit. Your host program cannot access the internal SQLCA. If you declare the SQLCA and SQLCODE (Pro*FORTRAN only), Oracle returns the same status code to both after every SQL operation.

Each of the five characters in a SQLSTATE value is a digit (0..9) or an uppercase Latin letter (A..Z). Class codes that begin with a digit in the range 0..4 or a letter in the range A..H are reserved for predefined conditions (those defined in SQL92). All other class codes are reserved for implementation-defined conditions. Within predefined classes, subclass codes that begin with a digit in the range 0..4 or a letter in the range A..H are reserved for predefined subconditions. All other subclass codes are reserved for implementation-defined subconditions. Figure 8 - 1 shows the coding scheme.

Table 8 - 6 shows how Oracle errors map to SQLSTATE status codes. In some cases, several Oracle errors map to the status code. In other cases, no Oracle error maps to the status code (so the last column is empty). Status codes in the range 60000 .. 99999 are implementation-defined.

Using the SQL Communications Area

The SQL Communications area (SQLCA) is a record-like data structure. Its fields contain error, warning, and status information updated by Oracle whenever a SQL statement is executed. Thus, the SQLCA always reflects the outcome of the most recent SQL operation. To determine the outcome, you can check variables in the SQLCA.

In host languages that allow both local and global declarations, your program can have more than one SQLCA. For example, it might have one global SQLCA and several local ones. Access to a local SQLCA is limited by its scope within the program. Oracle returns information only to the "active" SQLCA.

Note: When your application uses SQL*Net to access a combination of local and remote databases concurrently, all the databases write to one SQLCA. There is not a different SQLCA for each database. For more information, see "Concurrent Logons" .

When MODE={ORACLE|ANSI13}, the SQLCA is required; if the SQLCA is not declared, compile-time errors will occur. The SQLCA is optional when MODE={ANSI|ANSI14}, but you cannot use the WHENEVER SQLWARNING statement without declaring SQLCA. So, if you want to use the WHENEVER SQLWARNING statement, you must declare the SQLCA.

Note: If you declare SQLCODE instead of the SQLCA in a particular compilation unit, the precompiler allocates an internal SQLCA for that unit. Your host program cannot access the internal SQLCA. If you declare the SQLCA and SQLCODE (Pro*FORTRAN only), Oracle returns the same status code to both after every SQL operation.

When MODE={ANSI|ANSI14}, you must declare either SQLSTATE (see "Declaring SQLSTATE" ) or SQLCODE (see "Declaring SQLCODE" ) or both. The SQLSTATE status variable supports the SQLSTATE status variable specified by the SQL92 standard. You can use the SQLSTATE status variable with or without SQLCODE. See Table 8 - 3 and Table 8 - 4 for more information.

Declaring the SQLCA

To declare the SQLCA, simply include it (using an EXEC SQL INCLUDE statement) in your host-language source file as follows:

* Include the Oracle Communications Area (ORACA).
EXEC SQL INCLUDE ORACA
EXEC SQL INCLUDE SQLCA;

The SQLCA is used if and only if there is an INCLUDE of the SQLCA.

When you precompile your program, the INCLUDE SQLCA statement is replaced by several variable declarations that allow Oracle to communicate with the program.

Declaring the SQLCA in Pro*FORTRAN

In Pro*FORTRAN, the SQLCA must be declared outside the Declare Section, because it is a COMMON block. Furthermore, the SQLCA must come before the CONNECT statement and the first executable FORTRAN statement.

You must declare the SQLCA in each subroutine and function that contains SQL statements. Every time a SQL statement in one of the subroutines or functions is executed, Oracle updates the SQLCA held in the COMMON block.

Ordinarily, only the order and datatypes of variables in a COMMON-list matter, not their names. However, you cannot rename the SQLCA variables because the precompiler generates code that refers to them. Thus, all declarations of the SQLCA must be identical. For more information about declaring the SQLCA in Pro*FORTRAN, see the Pro*FORTRAN Supplement to the Oracle Precompilers Guide.

What's in the SQLCA?

The SQLCA contains the following runtime information about the outcome of SQL statements:

Key Components of Error Reporting

Error reporting depends on variables in the SQLCA. This section highlights the key components of error reporting. The next section takes a close look at the SQLCA.

Status Codes

Every executable SQL statement returns a status code to the SQLCA variable SQLCODE, which you can check implicitly with the WHENEVER statement or explicitly with your own code.

Status codes can be zero, less than zero, or greater than zero. See "SQLCODE" for complete SQLCODE descriptions.

Warning Flags

Warning flags are returned in the SQLCA variables SQLWARN(0) through SQLWARN(7), which you can check implicitly or explicitly. These warning flags are useful for runtime conditions not considered errors by Oracle. For example, when DBMS=V6, if an indicator variable is available, Oracle signals a warning after assigning a truncated column value to a host variable. (If no indicator variable is available, Oracle issues an error message.)

Rows-Processed Count

The number of rows processed by the most recently executed SQL statement is returned in the SQLCA variable SQLERRD(3), which you can check explicitly.

Speaking strictly, this variable is not for error reporting, but it can help you avoid mistakes. For example, suppose you expect to delete about ten rows from a table. After the deletion, you check SQLERRD(3) and find that 75 rows were processed. To be safe, you might want to roll back the deletion and examine the search condition in your WHERE clause.

Parse Error Offset

Before executing a SQL statement, Oracle must parse it, that is, examine it to make sure it follows syntax rules and refers to valid database objects. If Oracle finds an error, an offset is stored in the SQLCA variable SQLERRD(5), which you can check explicitly. The offset specifies the character position in the SQL statement at which the parse error begins. The first character occupies position zero. For example, if the offset is 9, the parse error begins at the tenth character.

By default, static SQL statements are checked for syntactic errors at precompile time. So, SQLERRD(5) is most useful for debugging dynamic SQL statements, which your program accepts or builds at run time.

because the column name JOB is misspelled. The value of SQLERRD(5) is 15 because the erroneous column name JIB begins at the sixteenth character.

If your SQL statement does not cause a parse error, Oracle sets SQLERRD(5) to zero. Oracle also sets SQLERRD(5) to zero if a parse error begins at the first character (which occupies position zero). So, check SQLERRD(5) only if SQLCODE is negative, which means that an error has occurred.

Error Message Text

The error code and message for Oracle errors are available in the SQLCA variable SQLERRMC. At most, the first 70 characters of text are stored. To get the full text of messages longer than 70 characters, you use the SQLGLM function. See "Getting the Full Text of Error Messages" .

SQLCA Structure

This section describes the structure of the SQLCA, its fields, and the values they can store.

SQLCAID

This string field is initialized to "SQLCA" to identify the SQL Communications Area.

SQLCABC

This integer field holds the length, in bytes, of the SQLCA structure.

SQLCODE

This integer field holds the status code of the most recently executed SQL statement. The status code, which indicates the outcome of the SQL operation, can be any of the following numbers:

0

Oracle executed the statement without detecting an error or exception.

> 0

Oracle executed the statement but detected an exception. This occurs when Oracle cannot find a row that meets your WHERE-clause search condition or when a SELECT INTO or FETCH returns no rows.

< 0

When MODE={ANSI|ANSI14|ANSI13}, +100 is returned to SQLCODE after an INSERT of no rows. This can happen when a subquery returns no rows to process.

Oracle did not execute the statement because of a database, system, network, or application error. Such errors can be fatal. When they occur, the current transaction should, in most cases, be rolled back.

SQLERRM

This integer field holds the length of the message text stored in SQLERRMC.

SQLERRMC

This string field holds the message text for the error code stored in SQLCODE and can store up to 70 characters. For the full text of messages longer than 70 characters, use the SQLGLM function.

Verify SQLCODE is negative

before you reference SQLERRMC. If you reference SQLERRMC when SQLCODE is zero, you get the message text associated with a prior SQL statement.

SQLERRP

This string field is reserved for future use.

SQLERRD

This array of binary integers has six elements. Descriptions of the fields in SQLERRD (called SQLERD in FORTRAN) follow:

SQLERRD(1)

This field is reserved for future use.

SQLERRD(2)

This field is reserved for future use.

SQLERRD(3)

This field holds the number of rows processed by the most recently executed SQL statement. However, if the SQL statement failed, the value of SQLERRD(3) is undefined, with one exception. If the error occurred during an array operation, processing stops at the row that caused the error, so SQLERRD(3) gives the number of rows processed successfully.

The rows-processed count is zeroed after an OPEN statement and incremented after a FETCH statement. For the EXECUTE, INSERT, UPDATE, DELETE, and SELECT INTO statements, the count reflects the number of rows processed successfully. The count does

not include rows processed by an update or delete cascade. For example, if 20 rows are deleted because they meet WHERE-clause criteria, and 5 more rows are deleted because they now (after the primary delete) violate column constraints, the count is 20 not 25.

SQLERRD(4)

This field is reserved for future use.

SQLERRD(5)

This field holds an offset that specifies the character position at which a parse error begins in the most recently executed SQL statement. The first character occupies position zero.

SQLERRD(6)

This field is reserved for future use.

SQLWARN

This array of single characters has eight elements. They are used as warning flags. Oracle sets a flag by assigning it a "W" (for warning) character value. The flags warn of exceptional conditions.

For example, a warning flag is set when Oracle assigns a truncated column value to an output host variable.

Note: While Figure 8 - 2 illustrates SQLWARN as an array, it is implemented in Pro*COBOL as a group item with elementary PIC X items named SQLWARN0 through SQLWARN7. The Pro*FORTRAN implementation is composed of the LOGICAL variables, SQLWN0 through SQLWN7.

Descriptions of the fields in SQLWARN follow:

SQLWARN(0)

This flag is set if another warning flag is set.

SQLWARN(1)

This flag is set if a truncated column value was assigned to an output host variable. This applies only to character data. Oracle truncates certain numeric data without setting a warning or returning a negative SQLCODE value.

To find out if a column value was truncated and by how much, check the indicator variable associated with the output host variable. The (positive) integer returned by an indicator variable is the original length of the column value. You can increase the length of the host variable accordingly.

SQLWARN(2)

This flag is set if one or more nulls were ignored in the evaluation of a SQL group function such as AVG, COUNT, or MAX. This behavior is expected because, except for COUNT(*), all group functions ignore nulls. If necessary, you can use the SQL function NVL to temporarily assign values (zeros, for example) to the null column entries.

SQLWARN(3)

This flag is set if the number of columns in a query select list does not equal the number of host variables in the INTO clause of the SELECT or FETCH statement. The number of items returned is the lesser of the two.

SQLWARN(4)

This flag is set if every row in a table was processed by an UPDATE or DELETE statement without a WHERE clause. An update or deletion is called unconditional if no search condition restricts the number of rows processed. Such updates and deletions are unusual, so Oracle sets this warning flag. That way, you can roll back the transaction if necessary

SQLWARN(5)

This flag is set when an EXEC SQL CREATE {PROCEDURE|FUNCTION|PACKAGE|PACKAGE BODY} statement fails because of a PL/SQL compilation error.

SQLWARN(6)

This flag is no longer in use.

SQLWARN(7)

This flag is no longer in use.

SQLEXT

This string field is reserved for future use.

PL/SQL Considerations

When your precompiler program executes an embedded PL/SQL block, not all fields in the SQLCA are set. For example, if the block fetches several rows, the rows-processed count, SQLERRD(3), is set to 1, not the actual number of rows fetched. So, you should rely only on the SQLCODE and SQLERRM fields in the SQLCA after executing a PL/SQL block.

Getting the Full Text of Error Messages

The SQLCA can accommodate error messages up to 70 characters long. To get the full text of longer (or nested) error messages, you need the SQLGLM function. If connected to Oracle, you can call SQLGLM using the syntax

SQLGLM(message_buffer, buffer_size, message_length);

where:

message_buffer

is the text buffer in which you want Oracle to store the error message (Oracle blank-pads to the end of this buffer).

buffer_size

is an integer variable that specifies the maximum size of the buffer in bytes.

message_length

is an integer variable in which Oracle stores the actual length of the error message.

The maximum length of an Oracle error message is 512 characters including the error code, nested messages, and message inserts such as table and column names. The maximum length of an error message returned by SQLGLM depends on the value you specify for buffer_size.

In the following example, you call SQLGLM to get an error message of up to 100 characters in length:

Notice that SQLGLM is called only when a SQL error has occurred. Always make sure SQLCODE is negative before calling SQLGLM. If you call SQLGLM when SQLCODE is zero, you get the message text associated with a prior SQL statement.

Using the WHENEVER Statement

With the WHENEVER statement you can specify actions to be taken when Oracle detects an error, warning condition, or "not found" condition. These actions include continuing with the next statement, calling a routine, branching to a labeled statement, or stopping.

You code the WHENEVER statement using the following syntax:

EXEC SQL WHENEVER <condition> <action>;

You can have Oracle automatically check the SQLCA for any of the following conditions.

SQLWARNING

SQLWARN(0) is set because Oracle returned a warning (one of the warning flags, SQLWARN(1) through SQLWARN(7), is also set) or SQLCODE has a positive value other than +1403. For example, SQLWARN(1) is set when Oracle assigns a truncated column value to an output host variable.

Declaring the SQLCA is optional when MODE={ANSI|ANSI14}. To use WHENEVER SQLWARNING, however, you must declare the SQLCA.

SQLERROR

SQLCODE has a negative value because Oracle returned an error.

NOT FOUND

SQLCODE has a value of +1403 (+100 when MODE={ANSI|ANSI14| ANSI13}), because Oracle could not find a row that meets the search condition of a WHERE clause, or a SELECT INTO or FETCH returned no rows. When MODE={ANSI|ANSI14|ANSI13}, +100 is returned to SQLCODE after an INSERT of no rows.

When Oracle detects one of the preceding conditions, you can have your program take any of the following actions.

CONTINUE

Your program continues to run with the next statement if possible. This is the default action, equivalent to not using the WHENEVER statement. You can use it to "turn off" condition checking.

DO

Your program transfers control to an internal routine. When the end of the routine is reached, control transfers to the statement that follows the failed SQL statement.

A routine is any functional program unit that can be invoked such as a COBOL paragraph or FORTRAN subroutine. In this context, separately compiled programs, such as COBOL subroutines, are not routines.

The usual rules for entering and exiting a routine apply. However, passing parameters to the routine is not allowed. Furthermore, the routine must not return a value.

Notice how the procedures check variables in the SQLCA to determine a course of action.

Scope

Because WHENEVER is a declarative statement, its scope is positional, not logical. It tests all executable SQL statements that follow it in the source file, not in the flow of program logic. So, code the WHENEVER statement before the first executable SQL statement you want to test.

A WHENEVER statement stays in effect until superseded by another WHENEVER statement checking for the same condition.

In the example below, the first WHENEVER SQLERROR statement is superseded by a second, and so applies only to the CONNECT statement. The second WHENEVER SQLERROR statement applies to both the UPDATE and DROP statements, despite the flow of control from step1 to step3.

Guidelines

The following guidelines will help you avoid some common pitfalls.

Placing the Statements. In general, code a WHENEVER statement before the first executable SQL statement in your program. This ensures that all ensuing errors are trapped because WHENEVER statements stay in effect to the end of a file.

Handling End-of-Data Conditions. Your program should be prepared to handle an end-of-data condition when using a cursor to fetch rows. If a FETCH returns no data, the program should branch to a labeled section of code where a CLOSE command is issued, as follows:

Avoiding Infinite Loops. If a WHENEVER SQLERROR GOTO statement branches to an error handling routine that includes an executable SQL statement, your program might enter an infinite loop if the SQL statement fails with an error. You can avoid this by coding WHENEVER SQLERROR CONTINUE before the SQL statement, as shown in the following example:

Maintaining Addressability. With host languages that allow local as well as global identifiers, make sure all SQL statements governed by a WHENEVER GOTO statement can branch to the GOTO label. The following code results in a compile-time error because labelA in FUNC1 is not within the scope of the INSERT statement in FUNC2:

Getting the Text of SQL Statements

In many precompiler applications, it is convenient to know the text of the statement being processed, its length, and the SQL command (such as INSERT or SELECT) that it contains. This is especially true for applications that use dynamic SQL.

The routine SQLGLS, which is part of the SQLLIB runtime library, returns the following information:

the text of the most recently parsed SQL statement

the length of the statement

a function code (see Table 8 - 8) for the SQL command used in the statement

You can call SQLGLS after issuing a static SQL statement. With dynamic SQL Method 1, you can call SQLGLS after the SQL statement is executed. With dynamic SQL Method 2, 3, or 4, you can call SQLGLS after the statement is prepared.

To call SQLGLS, you use the following syntax:

SQLGLS(SQLSTM, STMLEN, SQLFC)

Table 8 - 7 shows the host-language datatypes available for the parameters in the SQLGLS argument list.

Parameter

Language

Datatype

SQLSTM

COBOL

PIC X(n)

FORTRAN

CHARACTER*n

STMLEN, SQLFC

COBOL

PIC S9(9) COMP

FORTRAN

INTEGER*4

Table 8 - 7. Parameter Datatypes

All parameters must be passed by reference. This is usually the default parameter passing convention; you need not take special action.

The parameter SQLSTM is a blank-padded (not null-terminated) character buffer that holds the returned text of the SQL statement. Your program must statically declare the buffer or dynamically allocate memory for it.

The length parameter STMLEN is a four-byte integer. Before calling SQLGLS, set this parameter to the actual size (in bytes) of the SQLSTM buffer. When SQLGLS returns, the SQLSTM buffer contains the SQL statement text blank padded to the length of the buffer. STMLEN returns the actual number of bytes in the returned statement text, not counting the blank padding. However, STMLEN returns a zero if an error occurred.

The parameter SQLFC is a four-byte integer that returns the SQL function code for the SQL command in the statement. Table 8 - 8 shows the function code for each SQL command.

SQLGLS does not return statements that contain the following commands:

CONNECT

COMMIT

ROLLBACK

RELEASE

FETCH

There are no SQL function codes for these statements.

Code

SQL Function

Code

SQL Function

01

CREATE TABLE

39

AUDIT

02

SET ROLE

40

NOAUDIT

03

INSERT

41

ALTER INDEX

04

SELECT

42

CREATE EXTERNAL DATABASE

05

UPDATE

43

DROP EXTERNAL DATABASE

06

DROP ROLE

44

CREATE DATABASE

07

DROP VIEW

45

ALTER DATABASE

08

DROP TABLE

46

CREATE ROLLBACK SEGMENT

09

DELETE

47

ALTER ROLLBACK SEGMENT

10

CREATE VIEW

48

DROP ROLLBACK SEGMENT

11

DROP USER

49

CREATE TABLESPACE

12

CREATE ROLE

50

ALTER TABLESPACE

13

CREATE SEQUENCE

51

DROP TABLESPACE

14

ALTER SEQUENCE

52

ALTER SESSION

15

(not used)

53

ALTER USER

16

DROP SEQUENCE

54

COMMIT

17

CREATE SCHEMA

55

ROLLBACK

18

CREATE CLUSTER

56

SAVEPOINT

19

CREATE USER

57

CREATE CONTROL FILE

20

CREATE INDEX

58

ALTER TRACING

21

DROP INDEX

59

CREATE TRIGGER

22

DROP CLUSTER

60

ALTER TRIGGER

23

VALIDATE INDEX

61

DROP TRIGGER

24

CREATE PROCEDURE

62

ANALYZE TABLE

25

ALTER PROCEDURE

63

ANALYZE INDEX

26

ALTER TABLE

64

ANALYZE CLUSTER

27

EXPLAIN

65

CREATE PROFILE

28

GRANT

66

DROP PROFILE

29

REVOKE

67

ALTER PROFILE

30

CREATE SYNONYM

68

DROP PROCEDURE

31

DROP SYNONYM

69

(not used)

32

ALTER SYSTEM SWITCH LOG

70

ALTER RESOURCE COST

33

SET TRANSACTION

71

CREATE SNAPSHOT LOG

34

PL/SQL EXECUTE

72

ALTER SNAPSHOT LOG

35

LOCK TABLE

73

DROP SNAPSHOT LOG

36

(not used)

74

CREATE SNAPSHOT

37

RENAME

75

ALTER SNAPSHOT

38

COMMENT

76

DROP SNAPSHOT

Table 8 - 8. SQL Codes

Using the Oracle Communications Area

In the same way the SQLCA handles standard SQL communications; the Oracle Communications Area (ORACA) handles Oracle communications. When you need more information about runtime errors and status changes than the SQLCA provides, use the ORACA. It contains an extended set of diagnostic tools. However, use of the ORACA is optional because it adds to runtime overhead.

Besides helping you to diagnose problems, the ORACA lets you monitor your program's use of Oracle resources such as the SQL Statement Executor and the cursor cache.

In host languages that allow local as well as global declarations, your program can have more than one ORACA. For example, it might have one global ORACA and several local ones. Access to a local ORACA is limited by its scope within the program. Oracle returns information only to the "active" ORACA. The information is available only after a commit or rollback.

Declaring the ORACA

To declare the ORACA, simply include it (using an EXEC SQL INCLUDE statement) in your host-language source file as follows:

* Include the Oracle Communications Area (ORACA).
EXEC SQL INCLUDE ORACA

The ORACA must be declared outside the Declare Section.

When you precompile your program, the INCLUDE ORACA statement is replaced by several program variable declarations. These declarations allow Oracle to communicate with your program.

Enabling the ORACA

To enable the ORACA, you must specify the ORACA option, either on the command line with

ORACA=YES

or inline with

EXEC ORACLE OPTION (ORACA=YES);

Then, you must choose appropriate runtime options by setting flags in the ORACA.

What's in the ORACA?

The ORACA contains option settings, system statistics, and extended diagnostics such as

Choosing Runtime Options

The ORACA includes several option flags. Setting these flags by assigning them non-zero values allows you to

save the text of SQL statements

enable DEBUG operations

check cursor cache consistency (the cursor cache is a continuously updated area of memory used for cursor management)

check heap consistency (the heap is an area of memory reserved for dynamic variables)

gather cursor statistics

The descriptions below will help you choose the options you need.

ORACA Structure

This section describes the structure of the ORACA, its fields, and the values they can store.

ORACAID

This string field is initialized to "ORACA" to identify the Oracle Communications Area.

ORACABC

This integer field holds the length, expressed in bytes, of the ORACA data structure.

ORACCHF

If the master DEBUG flag (ORADBGF) is set, this flag lets you check the cursor cache for consistency before every cursor operation.

The Oracle runtime library does the consistency checking and might issue error messages, which are listed in Oracle7 Server Messages. They are returned to the SQLCA just like Oracle error messages.

This flag has the following settings:

0

Disable cache consistency checking (the default).

1

Enable cache consistency checking.

ORADBGF

This master flag lets you choose all the DEBUG options. It has the following settings:

0

Disable all DEBUG operations (the default).

1

Enable all DEBUG operations.

ORAHCHF

If the master DEBUG flag (ORADBGF) is set, this flag tells the Oracle runtime library to check the heap for consistency every time the precompiler dynamically allocates or frees memory. This is useful for detecting program bugs that upset memory.

This flag must be set before the CONNECT command is issued and, once set, cannot be cleared; subsequent change requests are ignored. It has the following settings:

0

Disable heap consistency checking (the default).

1

Enable heap consistency checking.

ORASTXTF

This flag lets you specify when the text of the current SQL statement is saved. It has the following settings:

0

Never save the SQL statement text (the default).

1

Save the SQL statement text on SQLERROR only.

2

Save the SQL statement text on SQLERROR or SQLWARNING.

3

Always save the SQL statement text.

The SQL statement text is saved in the ORACA subrecord named ORASTXT.

Diagnostics

The ORACA provides an enhanced set of diagnostics; the following variables help you to locate errors quickly.

ORASTXT

This subrecord helps you find faulty SQL statements. It lets you save the text of the last SQL statement parsed by Oracle. It contains the following two fields:

ORASTXTL

This integer field holds the length of the current SQL statement.

ORASTXTC

This string field holds the text of the current SQL statement. At most, the first 70 characters of text are saved.

Statements parsed by the precompiler, such as CONNECT, FETCH, and COMMIT, are not saved in the ORACA.

ORASFNM

This subrecord identifies the file containing the current SQL statement and so helps you find errors when multiple files are precompiled for one application. It contains the following two fields:

ORASFNML

This integer field holds the length of the filename stored in ORASFNMC.

ORASFNMC

This string field holds the filename. At most, the first 70 characters are stored.

ORASLNR

This integer field identifies the line at (or near) which the current SQL statement can be found.

Cursor Cache Statistics

The variables below let you gather cursor cache statistics. They are automatically set by every COMMIt or ROLLBACK statement your program issues. Internally, there is a set of these variables for each CONNECTed database. The current values in the ORACA pertain to the database against which the last commit or rollback was executed.

ORAHOC

This integer field records the highest value to which MAXOPENCURSORS was set during program execution.

ORAMOC

This integer field records the maximum number of open Oracle cursors required by your program. This number can be higher than ORAHOC if MAXOPENCURSORS was set too low, which forced the precompiler to extend the cursor cache.

ORACOC

This integer field records the current number of open Oracle cursors required by your program.

ORANOR

This integer field records the number of cursor cache reassignments required by your program. This number shows the degree of "thrashing" in the cursor cache and should be kept as low as possible.

ORANPR

This integer field records the number of SQL statement parses required by your program.

ORANEX

This integer field records the number of SQL statement executions required by your program. The ratio of this number to the ORANPR number should be kept as high as possible. In other words, avoid unnecessary reparsing. For help, see Appendix C.

An Example

The following program prompts for a department number, inserts the name and salary of each employee in that department into one of two tables, then displays diagnostic information from the ORACA: